This invention relates to an electrical termination system. More particularly, it relates to a telephone cable shield bond connector.
Telephone cable, particularly buried cable, often includes a metal shield which provides both mechanical and electrical protection for the primary conductors in the core. This metal shield surrounds the core and is particularly useful in insuring that lightning does not penetrate the core. In order to provide this electrical protection, the shield must be properly grounded. Thus, the shield must be terminated so it may be connected to a ground post, and so that the shields of adjacent cables may be spliced together by a jumper. Obviously, this termination must be very reliable.
A standard technique to terminate a shield is to punch a hole through the polyethylene jacket of the cable and through the shield and insert a threaded stud through the hole with the base of the screw head having serrations for penetrating into the shield. A nut is tightened down onto the stud and on to the polyethylene jacket, thus driving the serrations down into the shield and holding it in place. One of the problems with this type of termination system is that the polyethylene jacket tends to flow, even at relatively low temperatures, as what is known as cold flow. This permits the assembly to loosen, and, therefore, any electrical connection which is made to the assembly becomes unreliable. One such termination system is set forth in U.S. Pat. No. 4,023,882, which also uses a lock washer to secure the screw head.
Another cable shield bond device is disclosed in U.S. Pat. No. 3,857,994. This patent utilizes a rivet having serrations in the base for penetrating into the shield. The top of the rivet barrel is terminated to a rigid dome-shaped member which is further connected to an electrical jumper. The dome-shaped member and the base of the rivet compress a pair of rubber resilient members, which in turn maintain electrical contact between the serrated ring and the shield. The specification does not lead one to believe that the dome-shaped member is itself resilient.
U.S. Pat. No. 3,963,299 also shows a shield bond connector which utilizes a serrated plate for biting into the shield of the cable. A cover plate, which generally conforms to the shape of the cable, is terminated over the top of the cable and, along with a stud and screw combination, holds the serrated pressure plate in place.
In a field somewhat removed from shield bond connectors, U.S. Pat. No. 3,644,869 shows the use of a Belleville washer in an electrical connector assembly. The Belleville washer serves as a spring to provide connection forces.